SSH

SSH is a protocol to securely connect to a computer. Via SSH you can access the command line, just as if you connected to the computer with a monitor and a keyboard. By default, the Pi has SSH enabled.

Windows: SSH via Putty

You can download Putty from here. The Raspberry Pi Foundation has a quick introduction here.

Mac and Linux

On Mac and Linux, SSH is already installed and available within the terminal.

http://www.raspberrypi.org/documentation/remote-access/ssh/unix.md

To log into the Pi via ssh, type:

ssh pi@<ip-address>

Replace <ip-address> with the IP address of the Pi.

Copying a File to the Raspberry Pi

From the Command Line

If you want to copy a file to the Raspberry Pi form your PC, use the following command:

scp <filename> pi@<ip address of the pi>:~/

For example:

scp getmyip.jar pi@192.168.1.106:~/

This will copy the file into the home directory (/home/pi). During the process, you will be asked for the password for the username pi. If you did not change anything, that password is raspberry.